16-10 Effects of successive high severity fires on sediment yield and debris-flow volume

Session: Wildland Fire: An Agent of Geomorphic, Ecologic, and Societal Change

Presenting Author:

Authors:

Abstract:

Steep burned watersheds are more susceptible to debris flows than similar unburned areas. Moreover, debris-flow activity following a wildfire can have impactful negative effects on people, infrastructure, and aquatic habitats. In this study, we quantified the volume of sediment eroded from 21 small watersheds (0.12 km ² to 3.8 km²) during the first several months following the 2022 Pipeline Fire in northern Arizona, USA, using digital elevation models (DEM) derived from airborne lidar acquired before (16 August 2019) and after (12 October 2022) the fire. Most of the area was also burned by the 2010 Schultz Fire, which allowed us to examine the effects of successive moderate-to-high severity fire on sediment yield and debris-flow volume. A comparison of debris-flow volumes was conducted using a DEM of difference (DoD). The volume data from the DoDs showed that debris-flow volumes after the 2010 fire were smaller than volumes from areas that burned in both 2010 and 2022. This indicated that debris-flow volumes were magnified by the compound effects of the two fires. This result was supported by observations in the DoD that low soil burn severity in the twice-burned areas produced sediment yields similar to high soil burn severity areas in once-burned watersheds. These results illustrate the benefits of accounting for the influence of recent fire history in postfire assessments of sediment-related hazards.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10324

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